In any criminal prosecution for a violation of Section 10.45.020 of this chapter relating to driving a vehicle while under the influence of alcohol, the amount of alcohol in the defendant’s blood at the time alleged as shown by chemical analysis of the defendant’s blood, urine, breath, or other bodily substance, shall give rise to the following presumptions:

A. If there was at that time 0.05 percent or less by weight of alcohol in the defendant’s blood, it shall be presumed that the defendant was not under the influence of alcohol.

B. If there was at that time in excess of 0.05 percent but less than 0.10 percent by weight of alcohol in the defendant’s blood, such fact shall not give rise to any presumption that the defendant was or was not under the influence of alcohol, but such fact may be considered with other competent evidence in determining the guilt or innocence of the defendant. (Ord. 357 § 1, 1978)